Safety brake mechanism for externally powered automatic gun



J. G. ROCHA March 30, 1965 SAFETY BRAKE MECHANISM FOR EXTERNALLY POWERED AUTOMATIC GUN Filed Sept. 18, 1962 4 Sheets-Sheet 1 INVENTOR. J 0111 ELRU lfhu 1,4 m- $4217 fil z March 30, 1965 J. G. ROCHA 3,175,464

SAFETY BRAKE MECHANISM FOR EXTERNALLY POWERED AUTOMATIC GUN Filed Sept. 18, 1962 4 sheets-sheaf? L 1 :E E 1,, 1

INVENTOR. John [3.Ruc1111 March 1965 J. a. ROCHA 3, 75, 64

SAFETY BRAKE MECHANISM FOR EXTERNALLY POWERED AUTOMATIC GUN Filed Sept. 18, 1962 4 Sheets-Sheet 3 J. G. ROCHA March 30, 1965 SAFETY BRAKE MECHANISM FOR EXTERNALLY POWERED AUTOMATIC GUN 4 Sheets-Sheet 4 Filed Sept. 18, 1962 INVENTOR Juhn Er- Rn B1111 United States Patent John G. Rocha, Westfield, Mass, assignor to the United States of America as represented by the Secretary of the Army Filed Sept. 18, 1962, Ser. No. 224,565 9 Claims. (Cl. 89-161) (Granted under Title 35, US. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

This invention relates to automatic guns with longitudinally reciprocal barrels and is more particularly directed to safety mechanism for automatically halting the firing operation of the gun while the firing chamber in the barrel is still occupied by a fired cartridge case.

As more fully explained in my copending patent application for Motor Driven Automatic Gun, Serial No. 90,147, filed February 17, 1961, the rate of fire of this gun may be rapidly increased or decreased to meet changes in the particular conditions encountered in firing at various types of military targets. This has been accomplished by incorporating an independently operated electric motor to rotate a cylindrical drum provided with a cam track for continuously reciprocating the barrel into and out of battery position. A second cam track on the drum is utilized to successively feed the cartridges in a linked belt into position to be chambered by rearward movement of the barrel into battery position. The locking of the barrel and the subsequent actuation of the firing means is accomplished by a third cam track on the drum. It is, therefore, readily apparent that the feeding and firing of each cartridge is completely dependent upon the rotation imparted to the drum. Consequently, the rate of fire of the gun may be varied simply by changing the rotative speed of the drive motor.

Although the release of the gun firing trigger is designed to half further operation of the drive motor, the rotation of the drum will continue until the momentum imparted thereto is completely expended. During this period of decelerating movement, the rotation of the drum is frequently of sufiicient extent to feed a live cartridge into firing position and effect a partial chambering thereof by the barrel. As a result, any subsequent rotation which might be accidentally imparted to the drum could produce an unexpected and dangerous discharge of the cartridge in the firing position.

However, as more fully explained in my copending patent application entitled Feed Mechanism for Externally Powered Automatic Gun, Serial No. l'16,884 filed June 13, 1961, the release of the firing trigger is arranged to prevent further feeding movement of the cartridge belt. This is accomplished by actuating a solenoid to lift a suitable blocking member into the feeding path of the cartridges. A cam track on this member serves to pivot the cartridge feed pawl out of further engagement with the cartridge-belt. While such mechanism effectively prevents the termination of gun. operation with a live cartridge in firing position, the necessity for combining these additional components with the regular feed mechanism produces a relatively complex and expensive assembly. Furthermore, in order to reduce weight, the complete feed assembly is housed in a relatively thin and flexible sheet metal structure. It has been found that the vibration imparted thereto during operation of the gun is frequently of sufficient extent to actually misalign the various components in the feed mechanism. The possibility of dangerous and costly feed jams is even further enhanced 3,175,464 Fatented Mar. so, was

when the gun is being fired from vehicles such as tanks or helicopters.

Accordingly, it is an object of this invention to provide control means for terminating each burst of fire from an externally powered gun such that a fired cartridge casewill remain in the firing chamber of the barrel.

It is a further object of this invention to accomplish the aforesaid result without the necessity for increasing the complexity or the weight of the cartridge feed mechanism.

Another object of the present invention lies in the provision of means for halting the reciprocal movement of the barrel in an externally powered automatic gun prior to the replacement of the fired cartridge case by the next cartridge in the linked belt.

It is a particular purpose of this invention to provide an externally powered gun with a relatively simple and inexpensive brake mechanism which will be positively energized by each release of the firing trigger to halt a reciprocal barrel at a predetermined point in the firing cycle thereof.

The specific nature of the invention as well as other objects and advantages thereof will clearly appear from a description of a preferred embodiment as shown in the accompanying drawings in which:

FIG. 1 is an elevational view of an externally powered automatic gun and is partially sectioned to show the safety brake of this invention in the inoperative position;

FIG. 2 is a sectional view taken along line 2-2 of FIG. 1 to show the feed mechanism in greater detail;

FIG. 3 is an elevational view showing the brake in the compressed position required to halt the forward movement of the barrel;

FIG. 4 is a partial front end view of the gun with the brake in the barrel stopping position thereof;

FIG. 5 is a schematic diagram of the electrical firing circuit; and

FIG. 6 is an exploded perspective view of the safety brake mechanism.

As shown in FIG. 1, the gun in which the present invention is incorporated includes a receiver 12 with a forwardly opening bore 16 in which a barrel 14 is slidably mounted. A hollow cylindrical drum 18 is rotatably mounted between front and rear supports 20 and 22, respectively, which extend upwardly from receiver 12 and clockwise rotation is imparted to drum 18 by a variable speed motor 24 suitably mounted to rear drum support 22. Barrel 14 is formed with an upwardly projecting follower 26 arranged to engage in a continuous cam track 28 helically formed about the exterior periphery of drum 18. Thus, rotation of drum 18 is converted into reciprocal movement of barrel 14 from and toward battery position.

As drum 18 is rotated, a feed cam 30 in the rear face thereof actuates a pivotal feed arm 31 to bring a pivotal feed pawl 32 on the terminal end thereof into feeding engagement with the leading cartridge 34 in a linked belt 35. As a result, belt 35 is successively fed through a feed tray 36 suitably secured to the side of receiver 12 in axial alignment with a transverse feedway 38 therein. During this feeding cycle, the leading cartridge 34 is advanced into feedway 38 and positioned in alignment with the bore of barrel 14 by suitable holding pawls 40 as best shown in FIG. 2. After this cartridge is fired and as barrel 14 is moved forwardly out of feedway 38, the direction of travel of feed pawl 32 is reversed to pick up the next cartridge in the belt. During this portion of the feed cycle, the cartridge belt is held against retrograde movement by a suitable pawl 42 pivoted in the floor of feed tray 36. Thereafter, the cartridge belt is again advanced by feed pawl 32 and at the conclusion of the feedstroke is chambered by barrel 14. The continued rotation of drum 18 effects locking of barrel 14 in battery position and the firing of cartridge 34 as more fully described in my copending application Serial No. 90,147 filed February 17, 1961.

Although the release of firing trigger is arranged to simultaneously terminate the fiow of electrical current to drive motor 24, the feeding cycle of the leading cartridge in the belt is continued as the momentum of the rotating drum 18 is expended. Thus, since the operation of drive motor 24 may be halted at any point in the operating cycle of the gun, the deceleration of drum 18 may be sufficient to feed a live cartridge into firing position but insufficient to effect the actual firing thereof. This is a dangerous situation since drum 18 can be accidentally rotated independently of drive motor 24 and the firing mechanism actuated thereby.

However, it has been found that the possibility of such accidental firing can be entirely eliminated if the forward movement of barrel 14 is terminated before feed pawl 32 has been advanced sufiiciently to replace the fired cartridge case in feedway 38 with a live cartridge 34. In order to accomplish this desirable result, front drum support 26 is vertically slotted, as indicated at 44, to slidably receive a safety brake 46 for limited reciprocal movement in a vertical direction. Since the rear end of brake 46 is increased in width as shown at 48 in FIG. 6 to improve the structural rigidity thereof, slot 44 is formed with a mating T-shaped portion 50. The body of brake 46 is provided with a forwardly expanding opening 52 in the shape of an isosceles triangle with arcuate vertices. A vertical slot 54 extends upwardly from the upper leg of triangular opening 52 to terminate in a closed end 56 of arcuate configuration. A second vertical slot 58 of equal width and length but arcuately closed at both ends thereof is located below and forwardly of opening 52.

The lower end of brake 46 is formed with a cylindrical housing 66 having a forwardly opening bore 62 therein which is blocked by a threaded stud 64 locked in place by a transverse pin 66. The rear end of bore 62 is intersected by a slot 68 extending longitudinally along the underside of housing 60 to permit the insertion of a plunger '70 therein with a head 72 of substantially the same diameter as that of bore 62. A coil spring 74 is seated between plunger head 72 and stud 64 to normally urge plunger 70 into contact with the rear end wall of bore 62.

A rectangular rib 76 is formed along the top of barrel 14 of snfiicient width to freely enter longitudinal slot 68 in the underside of plunger housing 60 for engagement with the rear end of plunger head 72 as barrel 14 is moved forwardly subsequent to the discharge of cartridge 34 chambered therein. Thus, when safety brake 46 is lowered to bring slot 68 therein into alignment with rib 76 on barrel 14, the forward travel of the latter is buffered by the compression of coil spring 74 and effectively halted by the subsequent contact between plunger 70 and threaded stud 64.

Safety brake 46 is actuated by a rotary solenoid 78 having a cylindrical housing 80 and a central rotatable shaft 82 projecting outwardly therefrom. Shaft 82 is adapted to be rotated in a clockwise direction as viewed in FIG. 1 in response to the actuation of a gun firing trigger 83 in the form of a double pole, single throw switch spring-loaded in the open position. Trigger switch 83 may be located on the gun or remotely therefrom but in either case is electrically connected to solenoid 78 by leads 110. A rotary clock-type spring 84 surrounds shaft 82 and is secured thereto such that energy is stored therein as shaft 82 is rotated by solenoid 78. Thus, when solenoid 78 is inactivated by the opening of trigger switch 83, spring 84 serves to return shaft 82 to the original position thereof. A substantially triangular actuator 86 is fixedly secured at the larger end thereof to shaft 82 as by a key 88 and the opposite and smaller end thereof is arcuately narrowed, as indicated at 90, to fit into the rearmost vertex of triangular opening 52. A pair of threaded studs 92 project outwardly from solenoid housing on either side of shaft 82 and are respectively spaced to pass through vertical slots 54 and S8 of safety brake 46.

Front drum support 20 is provided with a pair of holes 94 spaced in axial correspondence with vertical slots 54 and 58 to permit the passage of solenoid studs 92 therethrough. A third hole 96 is centrally located between holes 94 to receive shaft 82 of solenoid 78. An internally threaded sleeve $8 is arranged to fit in each hole 94 and engage stud 92 therein for fixedly securing solenoid 7 8 to front drum support 20. The outer ends of each sleeve 98 are provided with an enlarged head 1% arranged to fit into holes 94 and slabbed, as indicated at 1&2 in FIG. 6, to permit the entry of a suitable wrench for rotating sleeves 98 to effect assembly or disassembly thereof from solenoid studs 92.

As shown in FIG. 5, one pole of trigger switch 83 is adapted for electrical connection with solenoid 78 while the other pole is similarly connected to a single throw relay 164 provided with double pole contacts 106 which, when closed, complete parallel circuits to drive motor 24 and to a microswitch 108 located on front drum support 29. Thus, when trigger switch 83 is closed to initiate a burst of automatic fire, solenoid 78 is energized to rotate shaft 82 in a clockwise direction and at the same time relay 194 is energized to close the circuit to drive motor 24 and microswitch 108. However, motor 24 will not begin to operate until actuator 86 is pivoted by solenoid shaft 82 to lift safety brake 46 and plunger housing 66 thereon out of the reciprocal path of rib 76 on barrel 14. This upward movement of safety brake 46 closes microswitch 168 to initiate rotation of drive motor 24.

Thus, as shown in FIG. 1, barrel 14 is free to reciprocate in response to the rotation of drum 18 and permits firing of the gun. Relay 1% includes a one-quarter second time deiay mechanism (not shown) which, in the event of any feed jam or other malfunction resulting in a stoppage of the recoiling parts, will open contacts 196 to terminate the overload status of motor 24 and prevent any serious damage thereto.

When trigger switch 83 is released to tie-energize solenoid 73, the one-quarter second time delay built into relay 194 will continue the fiow of electrical current to drive motor 24. During this period, spring 84 will pivot actuator 86 in the direction required to lower safety brake housing 60 into contact with the exterior surface of barrel 14. In the event rib 76 is positioned directly beneath plunger housing 60 when solenoid 78 is de-energized, the downward movement of safety brake 46 will be delayed until rib 76 is withdrawn from contact therewith during rearward movement of barrel 14 into battery position. Thereupon, the subsequent downward movement of safety brake 46 will open microswitch 108 to de-energize drive motor 24.

At this point, the rapidly rotating drum 18 possesses sufficient inertia to complete the rearward firing movement of barrel 14 as well as the return stroke thereof required to replace the fired cartridge case with the next cartridge in the belt. But as barrel 14 is moved forwardly, rib 76 thereon strikes the rear end of plunger 70, as shown in FIG. 3, whereupon the resulting compression of spring 74 terminates the forward movement of barrel 14 prior to the point at which the fired cartridge case will be ejected. Thus, the recoiling parts of the gun will never stop with a live cartridge in position to be chambered by barrel 14 in the event of any accidental movement which may be imparted thereto after drive motor 24 has ceased to operate.

It is, therefore, apparent that the present invention provides a safe and reliable means for halting the overtravel of drum 18 before the fired cartridge case is ejected by the feeding movement of the next cartridge in the belt. Furthermore, this safety device is an extremely compact unit which can be mounted in a relatively sturdy portion of the gun to avoid the feed jams heretofore encountered when the device for halting the feeding movement of the cartridges was contained in the relatively light and flexible feed tray 36 utilized in this gun.

Although a particular embodiment of the invention has been described in detail herein, it is evident that many variations may be devised within the spirit and scope thereof and the following claims are intended to include such variations.

I claim:

1. In a gun having a receiver, an externally powered drum rotatably mounted between front and rear supports extending from the receiver, a longitudinally slidable barrel, cam means on the drum for reciprocating the barrel between a rearward battery position and a fully forward cartridge feeding position, and feed means responsive to the rotation of the drum for successively advancing each cartridge in a linked belt into axial alignment with the bore of the barrel for chambering thereby during movement toward battery position, the combination of a stop on the barrel, buffer means slidably mounted in the front drum support for vertical movement into and out of the longitudinal path of said barrel stop, solenoid means responsive to each firing operation of the gun for lifting said buffer means out of the path of said barrel stop, and means responsive to the inactivation of said solenoid means for lowering said buffer means into the path of said barrel stop to halt the forward movement of the barrel and the corresponding rotation of the drum prior to the feeding advance of the leading unfired cartridge in the linked belt.

2. The combination defined in claim 1 wherein said buffer means comprises a safety brake slidably mounted in the front drum support for reciprocal movement at right angles to the longitudinal axis of the barrel, a 1ongitudinal plunger slidably disposed in the lower end of said safety brake, and spring means surrounding said plunger for resisting the forward movement thereof, said safety brake having an access opening in the rear end thereof for exposing the rear end of said plunger to contact by said stop on the barrel.

3. The combination defined in claim 1 wherein said buffer means is carried in a safety brake slidably mounted in the front drum support for reciprocal movement at right angles to the longitudinal axis of the barrel, and said solenoid means for lifting said buffer means comprises a housing fixedly secured to the front drum support, a rotatable shaft extending centrally of said housing and an actuator secured at one end thereof to the free end of said shaft, said safety brake having a substantially triangular opening therein for receiving said actuator whereby the pivotal movement imparted thereto by the rotation of said shaft positions said buflfer means into and out of the path of said barrel stop.

4. In a gun having a receiver, an externally powered drum rotatably mounted between front and rear supports projecting upwardly from the receiver, a longitudinally slidable barrel, cam means on the drum for reciprocating the barrel between a rearward battery position and a fully forward cartridge feeding position, and feed means responsive to the rotation of the drum for successively advancing each cartridge in a linked belt into position to be chambered during movement of the barrel into battery position, the combination of a rectangular rib extending longitudinally along the top of the barrel, a safety brake slidably disposed in the front drum support for vertical movement into and out of the path of said barrel rib, a spring-biased plunger longitudinally disposed in the bottom of said safety brake, a solenoid housing secured to the front drum support, a rotatable solenoid shaft projecting centrally from said housing, an actuator secured to the free end of said shaft in camming engagement with said safety brake, and a rotary spring surrounding said shaft and fastened thereto whereby the rotation of said shaft pivots said actuator to lift said safety brake plunger out of the path of said barrel rib and thereby Winds said spring to provide the energy required to subsequently pivot said actuator for lowering said safety brake plunger into position to halt the forward movement of the barrel thereby terminating the rotation of the drum prior to the feeding advance of the leading unfired cartridge in the belt.

5. The combination defined in claim 4 wherein said rectangular rib is located on the barrel to maintain contact with said safety brake when the barrel is in the fully forward position thereof.

6. The combination defined in claim 4 wherein said safety brake includes a substantially triangular opening and said actuator is formed to extend into one vertex of said opening and impart vertical movement to said safety brake.

7. The combination defined in claim 4 wherein a pair of threaded mounting studs project from said solenoid housing through the front drum support, said safety brake is provided with elongated vertical slots for the passage of said studs, and each stud is capped by an internally threaded sleeve to secure said solenoid housing to the front drum support.

8. In an automatic gun having a slidable barrel, a rotatable drum for reciprocating the barrel between a rearward battery position and a fully forward cartridge feeding position, a drive motor for rotating said drum, and trigger means for electrically initiating operation of the drive motor, the combination of a stop on the barrel, buffer means slidably disposed for vertical movement into and out of the longitudinal path of said barrel stop, solenoid means responsive to operation of the trigger means for lifting said buffer means out of the path of said barrel stop, spring means responsive to the release of the trigger means and the corresponding inactivation of said solenoid means for lowering said buffer means into the path of said barrel stop to halt the forward movement of the barrel, and switch means disposed in the vertical path of said buffer means for delaying the activation of the drive motor and the corresponding forward movement of the barrel until said buffer means is completely withdrawn from the longitudinal path of movement of said barrel stop.

9. The combination defined in claim 8 including a time delay relay for interrupting the electrical circuit to said drive motor in the event the rotation of the drum is halted in excess of a predetermined period of time.

References Cited by the Examiner FOREIGN PATENTS 697,076 9/53 Great Britain.

BENJAMIN A. BORCHELT, Primary Examiner. SAMUEL FEINBERG, Examiner. 

1. IN A GUN HAVING A RECEIVER, AN EXTERNALLY POWERED DRUM ROTATABLY MOUNTED BETWEEN FRONT AND REAR SUPPORTS EXTENDING FROM THE RECEIVER, A LONGITUDINALLY SLIDABLE BARREL, CAM MEANS ON THE DRUM FOR RECIPROCATING THE BARREL BETWEEN A REARWARD BATTERY POSITION AND A FULLY FORWARD CARTRIDGE FEEDING POSITION, AND FEED MEANS RESPONSIVE TO THE ROTATION OF THE DRUM FOR SUCCESSIVELY ADVANCING EACH CARTRIDGE IN A LINKED BELT INTO AXIAL ALIGNMENT WITH THE BORE OF THE BARREL FOR CHAMBERING THEREBY DURING MOVEMENT TOWARD BATTERY POSITION, THE COMBINATION OF A STOP ON THE BARREL, BUFFER MEANS SLIDABLY MOUNTED ON THE FRONT DRUM SUPPORT FOR VERTICAL MOVEMENT INTO AND OUT OF THE LONGITUDINAL PATH OF SAID BARREL STOP, SOLENOID MEANS RE- 